Screw Drive Design

ABSTRACT

A screwdriver drive design for a screwdriver features an engagement end that is complementary to a fastening element drive design for a fastening element to be screwed. The fastening element drive design includes at least two drive surfaces formed on the fastening element for transmission of a torque suitable for rotation with a tool in a first rotation direction and transition surfaces disposed between these drive surfaces. The transition surfaces form a guide surface for the tool when rotating the tool in the first rotation direction and upon engagement of the tool in the other rotation direction causes an axial outward displacement of the tool, wherein the transition surfaces are formed as outside surfaces, and wherein the outside of the fastening element, outside the transition surfaces and the drive surfaces, lies in a cylindrical jacket forming a recess.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/056,364, entitled “Screw Drive Design,” filed Apr. 20, 2011, thedisclosure of which is hereby expressly incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a drive design for screws, nuts or thelike.

BACKGROUND OF THE INVENTION

There are cases in which, for safety reasons, screws or nuts must besecured in a manner that rules out the loosening of said screw or nut.So far, it is standard in such cases to incapacitate the screw drivethat serves for the application of a tool after the screw has beenfastened. This can happen, for example, through boring or smashing theplug that then prevents the application of a tool into the drive design.There are also tear-off screws on which a predetermined breaking pointis provided, which gives way upon attaining the required torque. Allthese systems have the disadvantage that they require additionalmeasures and, in part, they must be handled pedantically. Moreover,tear-off screws pose the problem of corrosion.

A screw is already known, in which the rotation drive is provided withthree triangle-shaped contact surfaces in a recess of the screw head,respectively located in a radial plane. A special screwdriver can beused to drive in these screws, whereas, in the reversed direction ofrotation, the tool does not drive the screw (DE 3403063 A1).

The objective of the invention is to create a possibility of designingconnections to be established by means of screws, so that they can onlybe loosened with difficulty or if destroyed.

To meet this objective, the invention proposes a drive design with thefeatures of claim 1. The invention also proposes a drive design for anaccompanying tool. Further embodiments of the invention are the objectof dependent claims.

This means that one can rotate the fastening element in one direction,naturally the drive-in direction; however, torque transmission is notpossible in the reversed direction of rotation. This can be achieved,for example, in that the transition surfaces extend so obliquely thatthe force applied in the direction of rotation produces a forcecomponent that presses the tool out of the recess.

In a further embodiment of the invention, the transition surfaces thatserve for guiding the tool in the rotation drive can be formed asinwardly aligned inside surfaces. The tool therefore engages with themwith a radial outside part.

It is, however, also possible and within the scope of the invention thatthe transition surfaces are formed as radial outside surfaces. In thiscase, the tool grips on the outside surfaces.

Particularly, it can be made possible that the drive surfaces and thetransition surfaces are formed in a recess originating from the end faceof the fastening element. In this case, it relates to a screw, forexample, with which the end face of the screw head facilitates theaccess to the recess. In this case, the screw head of such a screwtherefore contains a recess in which at least two drive surfacessuitable for the transmission of torque are arranged for rotating with atool in a direction of rotation, between which transition surfaces aredisposed, which, upon engagement of the tool in the other direction,cause an axial displacement of the tool out of the recess.

In order to cause a particularly effective force transmission whendriving in the screw, in accordance with the invention it can beprovided that the drive surfaces are disposed in radial planes. Acertain deviation from the radial plane is also possible, so that, in afurther embodiment through the drive design, the invention proposes thatin a cross-section extending transversely to the axis of the screw thedrive surfaces lie respectively on a radius or extend parallel to oneanother.

With an even number of drive surfaces, it can be provided therefore inaccordance with the invention that the drive surfaces in a cross-sectionextending transversely to the axis of the screw through the drive designlie on a diameter or extend parallel to one another and on a diameter.

In a longitudinal section through the fastening element, the drivesurfaces extend preferably parallel to the axis or in the axis.

In a further embodiment of the invention, it can be made possible thatthe drive surfaces form a drive edge that extends obliquely to the axis,whereby the drive edges of all drive surfaces diverge in the directionof the end face of the screw head.

For example, the drive edges can extend between the wall of the recessand the bottom of the recess.

In accordance with the invention, it can be made possible that thetransition surfaces are formed as wedged surfaces, whereby the wedge isoriented such that, by introducing torque in the reverse screwingdirection, a force component is produced out of the recess.

Particularly, it can be made possible that the transition surfacesextend between the drive edge of a drive surface of the drive surfaceconnection with the bottom of the recess and the wall of the recess.

It has turned out to be particularly practical if the drive designcomprises an odd number of drive surfaces and transition surfaces.

In a further embodiment of the invention, it can be made possible thatthe recess at least partially features a decreasing cross-section in thedirection from the end face away from the screw head. This is reasonableparticularly in the case of countersunk screws.

In yet a further embodiment of the invention, it can be made possiblethat the recess is formed at least partially cylindrical. Such acylindrical recess can also serve to improve the guidance of a toolbetter than it would in a recess that decreases in cross-section rightfrom the beginning.

In accordance with the invention, it can be made possible that therecess runs in a pointed tip.

However, it is also possible and proposed by the invention that therecess features a bottom that is formed preferably plane.

In accordance with the invention, it can be made possible that the wallof the recess at least in an axial section lies on a cylindrical jacketsurface, particularly in a section originating from the end face of thescrew head.

The screwdriver also proposed by the invention features a free end thedrive design of which is formed complementarily to the drive design ofthe screw head.

Further features, details and advantages of the invention are derivablefrom the claims and abstract, whereby the wording in both is based onreference to the contents of the description, following description ofpreferred embodiments of the invention as well as of the drawing. Shownhereby:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 the perspective schematic view of the free end of a screwdriver;

FIG. 2 a partial section through a screw head;

FIG. 3 shows a schematic side view of the front end of a screwdriver;

FIG. 4 a representation corresponding to FIG. 3;

FIG. 5 a schematic representation of the recess in a screw head;

FIG. 6 a representation corresponding to FIG. 5 of a modifiedembodiment;

FIG. 7 the side view of the front end of a screwdriver;

FIG. 8 a representation corresponding to FIG. 7 of a modifiedembodiment;

FIG. 9 the side view of a screwdriver bit;

FIG. 10 the end face view of the screwdriver bit of FIG. 9;

FIG. 11 a side view of a screw;

FIG. 12 a perspective representation of the front end of the screwdriverbit;

FIG. 13 a further perspective representation of a nut;

FIG. 14 an axial section through the nut of FIG. 13;

FIG. 15 a plan view of the nut of FIGS. 13 and 14;

FIG. 16 a representation of a further embodiment;

FIG. 17 an axial section through the nut of FIG. 16;

FIG. 18 a plan view of the nut of FIGS. 16 and 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a perspective view of the front end of a screwdriver thatfeatures a circular cylindrical shaft 1. Because the drive design of thescrew and screwdriver are formed complementarily to each other, however,the drive design of different surfaces can be represented better on asurface disposed outwardly such as on a screwdriver than in a recess,the following two types of representation are used. On the shaft 1 ofthe screwdriver, the drive surfaces 2 are formed, which lie in a radialplane. The drive surfaces 2 are limited, on the one hand, through thecylindrical outside of the shaft 1 and form an edge 3 at that point. Theconical tip of the screwdriver shaft 1 then forms a second edge 4 withthe drive surface 2 that is designated as a drive edge in the followingpassage. The drive surfaces 2 extend therefore from the outside of theshaft on the edge 3 into the material of the screwdriver shaft 1.

From the drive edges 4, transition surfaces 5 then extend, which form aboundary line 6 with the outside of the shaft 1. They extend thereforefrom the drive edge 4 aligned forward respectively on a drive surface tothe opposite end of the drive surface 2. Viewed from the side, thetransition surfaces 5 thus form wedged surfaces, while the drivesurfaces 2 lie in radial planes.

If one rotates the screwdriver around its longitudinal axis, the drivesurfaces 2 produce torque in rotation direction for a clockwiserotation, while for counterclockwise rotation the transition surfaces 5produce a force component also in axial direction. Based on theembodiment of the transition surfaces 5, this force component in axialdirection is greater than the force component in circumferentialdirection. Because the part of the drive surfaces 2 directly in the tip7 section can contribute only slightly to the transmission of torque,this tip can be flattened out in accordance with the invention, forexample in the form of a plane end face.

FIG. 2 shows a section through a screw head. It relates to a countersunkhead. Starting from a plane end face 8, a recess 9 is accommodated inthe screw head. The recess 9, in its section adjoining the end face 8directly, has a cylindrical cross-section or a cylindrical wall 10 thatis visible in the section. On this section, a section then adjoins inthat the wall 11 of the recess 9 lies on a conical surface, thus itcontinuously decreases inwards of the recess. The recess is closed by abottom 12.

In the recess, inward protrusions are formed, which are complementary tothe arrangement of the surfaces, as shown in FIG. 1. Drive surfaces 13are therefore provided, which extend between the bottom 12 and the wall10 in the recess. These drive surfaces 13 also lay in a radial planehere. They form drive edges 14 on the inwardly aligned side,corresponding to the drive edges 4 of the tool in FIG. 1. The transitionsurfaces 15 extend from the drive edges 14 of the drive surfaces 13.These form a connection with the wall 10 of the recess. In addition,here, the transition surfaces 15 extend in a wedge-shaped form, from theoutside edge 16 away from the drive edge 14 of every drive surface 13,from the drive surface 13 to the drive edge 14 of the next drive surface13.

In FIG. 1, it was already mentioned that the transition surfaces 5 forman edge 6 with the outside of shaft 1. Such an edge 6 is also formed bythe transition surfaces 15 in the recess. FIGS. 3 to 6 now show howthese transition edges 6, which also define the form of the transitionsurfaces 5, can be designed.

FIG. 3 represents a possibility whereby the edge 6 forming thetransition surfaces 5 is convex-shaped outwardly. With this, also thetransition surfaces 5 are wedge-shaped and convex.

In the embodiment according to FIG. 4, the transition edge 6 extendsconcave-shaped, which means that the transition surface 5 is also formedconcave.

FIGS. 5 and 6 show a plan view of drive designs whereby it can relateboth to the drive design of a tool as well as to the drive design of adriven screw. The drive surfaces 2 and/or 13 are designated here bytheir/its drive edges 4 on the screwdriver and/or 14 in the recess. Adrive should occur towards the arrow 17. Respectively two drive edges 4extend parallel to one another and parallel to a diameter, whereby inthe arrangement of FIG. 5 the drive edges 4 in drive direction lie infront of the diameter, while in the drive design of FIG. 6 the driveedges 4 lie respectively behind the diameter, to which they jointlyextend in parallel.

With reference to FIG. 1, it was mentioned that the drive surfaces 2 liein a radial plane. This is to ensure that the torque is transmitted inrotational direction. However, deviations are also possible from thisradial plane, as far as it is made possible that forces in anotherdirection are negligibly small or do not disturb as it does in therotational direction. FIG. 7 now shows an arrangement in which the drivesurface 2 turns back behind a radial plane, so that a force component isproduced into the recess 9 of the screw. This force component however isnegligibly small.

FIG. 8 shows an embodiment, in which the drive surface 2 lies in frontof the radial plane, whereby also here a certain force component isproduced in axial direction, which is likewise negligibly small. Such asolution as shown in FIG. 8 could be easier to produce than an exactradial plane.

FIG. 9 now shows the side view of a screwdriver bit that can be used ina conventional screwdriver. At the free end opposite the hexagon end,the screw bits feature an embodiment as it was indicated in FIG. 3,figure and FIG. 8. Here the drive surfaces 2 lie in a plane in front ofa radial plane, corresponding to FIG. 8.

FIG. 10 shows the view of the screwdriver bit of FIG. 9 from the bottomin FIG. 9, similar to FIGS. 5 and 6. You can also see from this thatfive drive edges 4 are provided, which are uniformly distributed overthe circumference.

FIG. 11 now shows a screw with a recess head, in the drive recess 9 ofwhich the surfaces are formed as they are complementary to theembodiment of the screwdriver bit in FIG. 9.

FIG. 12 shows the front end of the screwdriver bit of FIG. 9 in anisometric representation, with the drive surfaces 2, the transitionsurfaces 5, the drive edges 4 and the front star-shaped flat face end 18which corresponds to the bottom 12 of the screwdriver recess 9 of FIG.2.

While the previous figures deal with the representation of screws andaccompanying tools, the following figures show nuts that are madeaccording to the same principle.

FIGS. 13 to 15 show a nut in which the form of the transition surfaces15 and drive surfaces 13 are formed in the same manner as in the screwaccording to FIG. 2, with the only difference that instead of a planebottom 12, here the thread boring 20 is provided.

FIG. 16 shows again another embodiment of a nut. From an end-face 27, athread boring 20 goes through the nut. From the circumference of thethread boring 20, a series of drive surfaces 13 extends radial outwards,and between the drive surfaces 13, the transition surfaces 15 serving asguide surfaces extend. Outside the transition surfaces 15, the outside28 of the nut features a cylindrical jacket, see also FIG. 17.

The represented exemplary embodiments relate to screws and nuts, as wellas to the respectively complementary tools formed for these purposes.Naturally, there are also corresponding tools for the nuts with thesurfaces disposed on the outside, however, which are not representedindividually.

Obviously, also a screw head can feature an embodiment like the nuts inFIGS. 13 to 18 show.

1. A screwdriver drive design for a screwdriver the engagement end ofwhich features a form that is complementary to a fastening element drivedesign for a fastening element to be screwed, the fastening elementdrive design comprising at least two drive surfaces formed on thefastening element for transmission of a torque suitable for rotationwith a tool in a first rotation direction; and transition surfacesdisposed between these drive surfaces, which form a guide surface forthe tool when rotating the tool in the first rotation direction and uponengagement of the tool in the other rotation direction causes an axialoutward displacement of the tool, wherein the transition surfaces areformed as outside surfaces, and wherein the outside of the fasteningelement, outside the transition surfaces and the drive surfaces, lies ina cylindrical jacket forming a recess.
 2. The screwdriver drive designaccording to claim 1, wherein the transition surfaces are formed asinwardly aligned inside surfaces.
 3. The screwdriver drive designaccording to claim 1, wherein the transition surfaces of the fasteningelement drive design are formed as outside surfaces.
 4. The screwdriverdrive design according to claim 1, wherein the drive surfaces of thefastening element drive design are disposed in radial planes.
 5. Thescrewdriver drive design according to claim 1, wherein the drivesurfaces of the fastening element drive design lie in a cross-sectionthrough the fastening element drive design respectively on a radius orparallel to a radius.
 6. The screwdriver drive design according to claim1, wherein in an even number of drive surfaces respectively two drivesurfaces of the fastening element drive design extend in thecross-section of a diameter or parallel to a diameter.
 7. Thescrewdriver drive design according to claim 1, wherein the drivesurfaces of the fastening element drive design extend in a longitudinalsection through the drive design parallel to the axis of rotation or inthe axis of rotation.
 8. The screwdriver drive design according to claim1, wherein the drive surfaces of the fastening element drive design forma drive edge, whereby the drive edges of all drive surfaces diverge inthe direction of the end face of the fastening element for a drivedesign formed in a recess and converge for a drive design formed on theoutside.
 9. The screwdriver drive design according to claim 1, whereinthe transition surfaces of the fastening element drive design are formedas wedge-shaped surfaces.
 10. The screwdriver drive design according toclaim 9, wherein the transition surfaces of the fastening element drivedesign extend between the drive edge of a drive surface, the connectionof the drive surface with the bottom of the recess and the wall of therecess.
 11. The screwdriver drive design according to claim 1, with anodd number of drive surfaces and transition surfaces in the fasteningelement drive design.
 12. The screwdriver drive design according toclaim 1, wherein the recess of the fastening element drive design atleast partially features a decreasing cross-section in the directionaway from the end face the screw head.
 13. The screwdriver drive designaccording to claim 1, wherein the recess of the fastening element drivedesign is partially at least formed cylindrical in shape.
 14. Thescrewdriver drive design according to claim 1, wherein the recess of thefastening element drive design converges into a pointed tip.
 15. Thescrewdriver drive design according to claim 1, wherein the recess of thefastening element drive design features a particularly plane bottom.